1. Field of the Invention
This application is directed to a novel process of making sulfurized olefins, e.g., sulfurized isobutylene and to lubricant compositions containing such sulfurized isobutylene.
The metal surfaces of machinery or engines operating under heavy loads wherein metal slides against metal may undergo excessive wear or corrosion. Often the lubricants used to protect the metal surfaces deteriorate under such heavy loads and as a result, do not prevent wear at the points of metal to metal contact. Consequently, the performance of the machine or engine will suffer, and in aggravated cases the machine or engine may become completely inoperative.
There have been many attempts to devise additive systems which would provide satisfactory protection, but these have not always been successful. Furthermore, some of these additives are mixed with undesirable and/or malodorous by-products.
Sulfurized olefins have been extensively used in many lubricant applications requiring extreme pressure/antiwear activity. These sulfurized olefins which include sulfurized C.sub.3 -C.sub.8 olefins such as isobutylene are described by A. G. Horodysky in U.S. Pat. Nos. 3,703,504; 3,703,505; and 3,873,454. These patents and U.S. Pat. No. 4,240,958 generally employ methods of preparing their sulfurized products wherein the olefin is sulfohalogenated with a sulfur halide at some stage in their synthesis.
The direct sulfurization of olefins such as triisobutylene with sulfur is described, for example, in U.S. Pat. Nos. 2,995,569 and 3,796,661. These patents describe the formation of predominantly dithiol-thione type compositions made at elevated temperatures at both low and elevated pressures. U.S. Pat. No. 4,194,980 discloses cyclic sulfurized olefins prepared by reacting an olefin with a cyclic polydisulfide. U.S. Pat. Nos. 3,345,380 and 2,535,706 describe methods of making various thiones by reacting elemental sulfur and unsaturated hydrocarbons.
Sulfurized olefins have also been prepared by the direct sulfurization of olefins with sulfur and hydrogen sulfide, see U.S. Pat. Nos. 2,337,473; 4,119,549; 4,119,550; 4,191,659; 4,344,854 and 4,147,640. U.S. Pat. No. 4,147,640, for example, describes the sulfurization of various olefinic hydrocarbons such as dicyclopentadiene with sulfur and hydrogen sulfide.
Thus, it is well known that many methods have been used for producing organic sulfides by treating olefins. It is also well known that many sulfurized organic compositions are useful as lubricant additives. Typically the prior art processes provide sulfurized products having undesirably high levels of thiones, such as dithiol-thiones (or dithiolethiones), and high levels of thiones in combination with various complex sulfurized mixtures. Typically also these processes which are expensive and difficult to control provide products having a highly disagreeable odor. However, the specific and significantly improved discreet compositions produced by the narrowly defined processing conditions disclosed herein provide thermally and oxidatively stable, non-corrosive, low-odor, extreme pressure/antiwear additives for lubricating oils, greases and fuels.
U.S. Pat. No. 4,191,659 to Davis claims a method of making sulfurized compounds by contacting olefinic feedstock with sulfur, hydrogen sulfide and an ammonia or amine catalyst.
U.S. Pat. No. 4,119,550 to Davis et al. claims a method of preparing sulfurized compounds by contacting an olefinic feedstock with sulfur and hydrogen. The olefin can be isobutene and the catalyst can be ammonia or an amine.
U.S. Pat. No. 4,119,549 to Davis claims a method of making sulfurized materials by contacting olefinic compounds with sulfur and hydrogen sulfide. Isobutene is disclosed as a suitable olefin and the catalyst can be an amine or ammonia.
Dithiolethione-free sulfurized olefin compositions have been prepared by the reaction of sulfur, isobutylene and hydrogen sulfide as exemplified by U.S. Pat. No. 4,344,854 to Davis et al. noted above.
The above-identified '659, '549, '550 and '854 patents "require" that hydrogen sulfide be added in specified proportions as a "separate and distinct" reactant.
The use of sulfurized olefins has been well-known for their extreme-pressure and antiwear properties when formulated into lubricants, as exemplified, for example, by U.S. Pat. No. 3,703,504 to Horodysky noted above.
It has now been discovered that the reaction of sulfur and isobutylene in the presence of an aqueous strong base produces a non-staining, low odor, sulfurized isobutylene product having EP-active characteristics and suitable for use as for example a gear oil additive.